Control system forming a logic display

ABSTRACT

A sequence control system having switching and output modules arranged on a mounting member to form a ladder network which displays and implements the control logic appearing on a ladder drawing of the control system. The mounting member utilizes a ladder-shaped structure having contact and output modules mounted on the structure legs and powered through the struts connecting these legs. Each contact module is an AND gate having displayed on its face the normal state of the contacts it represents and the controlling element of that module. Each output module is a driver element having displayed on its face the element it controls. The modules are arranged according to a ladder drawing which drawing is displayed by the sum total of the module faces when the control system is assembled.

[52] US. Cl ..317/135, 317/262 R, 307/43 United States Patent 1191Vaughn CONTROL SYSTEM FORIVHNG A LOGIC DISPLAY Arthur L. Vaughn,Warren,.0hio

[73] Assignee: Bailey Meter Company, Wickliffe,

Ohio

22 Filed: Feb. 17, 1972 21 Appl. No.: 227,112

[75] Inventor:

307/149, 3l7/DIG. 9 [51] Int. Cl. ..L ..H02j

[58] Field of Search..... ..317/l35, 262 R, 101 CC, 317/122; 307/43,85-87, 149

[56] i References Cited UNITED STATES PATENTS 2/1971 Pastore ..307/l49Primary Examiner-L. T. Hix Attorney-Joseph M. Maguire Apr. 10, 1973 [57]ABSTRACT A sequence control system having switching and output modulesarranged on a mounting member to form a ladder network which displaysand implements the control logic appearing on a ladder drawing of thecontrol system.

The mounting member utilizes a ladder-shaped structure having contactand output modules mounted on the structure legs and powered through thestruts connecting these legs.

Each contact module, is an AND gate having displayed on its face thenormal state of the contacts it represents and the controlling elementof that module.

Each output module is a driver element having displayed on its face theelement it controls. The modules are arranged according to a ladderdrawing which drawing is displayed by the sum total of the module faceswhen the control system is assembled.

9 Claims, 5 Drawing Figures POWER SUPPLY PATENTED APR 1 01975 SHEET 1 BF2 AND GATE FIG 3 26 DRIVER SHEET 2 OF 2 :mnSw E38 CONTROL SYSTEM FORMINGA LOGIC DISPLAY BACKGROUND OF THE INVENTION 1. Field of the InventionThis invention relates to control systems in general and moreparticularly to small, sequence control systems having a limited inputand output range which systems do not warrant the complexity of aprogrammable memory.

2. Description of the Prior Art A sequence control system is generallydesigned and depicted, by those familiar with the art, in the form of aladder drawings. This is the standard representation of a machinecontrol and is the symbolic representation of the relays, outputdevices, and contacts used to implement the logic of the control system.

In detail, the vertical lines of the ladder drawing represent powerinput lines. Contacts appear along the horizontal lines of this drawingand indicate logical AND functions. All these contacts must be closed toallow power to be applied to an output device which is represented by acircle on the extreme right of the horizontal line. These contacts maybe any combination of both normally open and normally closed contacts.Normally open contacts are indicated by open lines. Normally closedcontacts are indicated by a diagonal slash appearing across the normallyopen contact symbol described previously.

Logical OR functions are indicated by a connecting line betweenhorizontal lines of the ladder drawing. This shows a parallel connectedflow of logic to the output device. Contacts along either parallelbranch when all closed, up to the junction point, will AND with themodules appearing after the junction point, which when closed, willactivate the output device.

Traditionally relays have been used to implement the sequence controlindicated by the ladder drawing. Relays are available in a variety ofconfigurations, however, all are characterized by a coil and a movablearmature which opens and closes output contacts. Each relay is energizedby a logical combination of inputs which allow power to be applied tothe coil under the right conditions to activate the output contacts. Theoutput contacts of the relay are used in the control system to activatecertain variables causing an orderly sequence of control operations.

Although the relay system is wired from a ladder drawing, there is nocorrelation between the physical arrangement of relays and contacts andtheir symbolic layout on a ladder drawing. This is due to all thecontacts of a relay and the coil being a part of the same physicaldevice. Thus troubleshooting and replacement of a faulty relay isdifficult and time consuming since cross-reference drawings are neededto locate the relays associated with the faulty logic. Also, despite thefact that relays are reliable, they are subject to sticking contacts andmechanical failures. Further, relay life is of short duration and doesnot warrant their reuse when I a control system is redesigned.

In recent times, solid state and fluidic logic components have beendeveloped which are used in control systems. These components offerincreased reliability and life since they are not subject to stickingcontacts and other mechanical frailties exhibited by relays. However thecontrol systems utilizing these components are nevertheless in a formatthat is not readily ladder drawing. Thus the logic display is in theappropriate language used and not as a ladder drawing.

The present invention contemplates new and improved apparatus, theutilization of which apparatus overcomes all the above referred toproblems and others and provides a control system which is easilyoperated and which corresponds directly to the control system ladderdrawing.

SUMMARY OF THE INVENTION In accordance with the present invention, thereis provided a sequence control system in the form of a ladder shapednetwork of either fluidic or electric contact and output modules. Thiscontrol system performs combinational logic functions on various systeminput and output signals to allow an orderly succession of functions asrequired by the control system.

The arrangement of the control system is such that a ladder drawing ofthe contact states which allow the various system outputs to beenergized is displayed by the ladder network of the control system. Thisis accomplished by having each ladder network contact module act like aswell as display the corresponding contact notation of the ladder drawingfor that control system. Each network output module acts like anddisplays the corresponding relay coil or output device notation of theladder drawing for that control system. Further the actual output stateof each module is displayed by an on off condition indicator connectedto the output of each module. Thus when the module is providing anoutput signal, the indicator is on, and when there is no module outputthe indicator is off.

The control system contact modules are logic AND gates havingcounterparts familiar to both persons skilled in the electric as well asfluidic arts. Thus the control system can be either electric or fluidic.The output modules could be any power driving means familiar to thoseskilled in the electric and fluidic arts such as DC to AC converters orstandard electric amplifiers for the electric control system and boosterrelays or pressure to electric converters for the fluidic controlsystem. Similarly those familiar with the art could choose anywell-known indicating means as a light emitting diode to be used as theindicator for the electrical system, while for a fluidic control systema two color, pressure activated flag could be used. Regardless of thesystem being electric or fluidic, each contact module will include oneinput, one control signal, one output and a contact display on its frontface corresponding to the ladder drawing contact for which it is acting.Similarly each output module will include one input, one output and adisplay on its face of the system control element it controls.

The arrangement of this sequence control system causes a display of aladder drawing of the control system whileat the same time functioningidentically to the ladder drawing. A view of the control systemdisplays. a labeled ladder drawing of the control system. This is atremendous aid in not only wiring but troubleshooting the system.

Further in accordance with the invention there is provided a contactmodule suitable for use in the above described sequence control system.This module pro- I provided an output module suitable for use in theabove described sequence control system. This module converts an inputsignal to anoutput signal capable of controlling an output element.Furthermore it has a legendon its face indicating the output element itcontrols as well as its input. This allows the output module not only tofunction as the output element of the ladder drawing of the sequencecontrol system but also displays the ladder drawing elementitcorresponds to.

Since these modules are logic AND gates and long life amplifiers,the'sequence control system may be dismantled and the parts reused aswell as making the system programmable merely by rearranging the contactand output modules according to a new ladder drawing of the new controlsystem.

Further in accordance with the invention there is provided a modulemounting frame in the form'of a ladder to which thepreviously. describedcontact and output modules may be mounted. The struts provide mountingfor the modules as well as supplying the power to the modules. The mainstructures supporting the struts provide rigidity to the control systemas well as providing the system power which is distributed to the strutsof the mounting frame. This mounting frame allows the modules to beassembled onto it in a manner that displays a ladder drawing of thecontrol system when the frame is viewed. The control system may bereprogrammed merely by rearranging the contact and output modules inconformity to the ladder drawingof the control system desired.

Thus the principal object of the invention is to provide a sequencecontrol system arranged and acting in the manner of the ladder drawingof the system.

Another object of the invention is to provide a sequence control systemwhich also indicates the inb dividual output state of its components byan indicator work to act like and display a ladder drawing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 depicts a generally acceptedmethod of depiction of a control system in the form of a ladder drawing.FIG. 2 depicts a sequence control system ladder network corresponding tothe ladder drawing of FIG. 1.

FIG. 3 depicts a normally open contact -module utilizing an AND gate.

FIG. 4 depicts a normally closed contact module utilizing an gate and aninverter. I I FIG. 5 depicts an output module utilizing a driver.

' DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawingswherein the showings are for the purpose of illustrating the preferredembodiment of the invention only and not for the purpose of limitingsame, FIG. 1 shows a ladder drawing 10 of a sequence control systemwhich activates circled output devices or relays 1CR and 2CR by acombination of the contacts 3L8, SCR, 9CR, 3CR and 2PS, 4CRrespectively. I

Moreparticularly the relay 1CR is activated by, the

logical combination of contact 31.8 and contact SCR I AND contact 9CR ORcontact 3CR AND contact 9CR. Similarly relay 2CR is activated by thelogical combination of contact 2PS AND contact 4CR. It will beunderstood that the number of branches as well as the number andcombination of contacts depends entirely on the requirements of thecontrol system.

Referring now to FIG. 2, a sequence control. system ladder network 20,which can be either electric or fluidic, has network fluidic power inputlines 22, within the vertical bars 33, between which are connectedmodule mounting bars 26a, 26b, 26c in a manner that allows the power tobe distributed .to the bars 26. Normally-open contact modules 28,normally-closed contact modules 30, and output modules 32 are operablymounted on the mounting bars 26 at power output points 21 which powerthe modules. The mounting is in a one-to-one position and functioncorrespondence to the contacts and output devices or relays in theladder drawing set forth in FIG. 1. The modules 28, 30, 32 all havemodule output indicators 31 which indicate the presence and absence ofan output signal from the corresponding modules. The indicators 31 canbe neon bulbs or light emitting diodes in electric networks, and twocolor pressure activated flag indicators for fluidic networks, or othersimilar devices which are known by those familiar with the respectivearts. The front of each normally open and normally closed contactmodules 28, 30, have symbols 34, 36, respectively indicating the type ofcontact function employed by the modules (normally open, normallyclosed). These drawings are in standard notation known to those familiarwith the art of control systems. The output modules32 have circles 38 ontheir front face, within which are indicated alphanurnerically themachine function controlled by the respective output module. Eachcontact module also has an alphanumeric representation on its face ofthe contact on the ladder drawing 10 it corresponds to. Thisalphanumeric representation also indicates the pilot device from whichthat particular contact module derives its control signal. It is thusseen that by viewing the ladder network 20 along with the front faces ofthe modules 28, 30, 32

a ladder drawing as set forth in FIG. 1 is displayed by the network 20.

In operation, the various contact modules receive control signals fromtheir respective pilot devices 19 by way of lines 25. These pilotdevices take the form of limit switches, level switches and relaycontacts as well as other devices familiar to those skilled in the art.Contact modules also receive input signals from other modules and pushbutton or selector switches from control operators. The normally-opencontact modules require a true signal both from their input lines aswell as their control lines to activate their outputs. The contactmodules are powered by supply connections (not shown) from the laddernetwork 20 as is well known to those skilled in the art. Thus in modulemounting bar 26a, module 3LS will produce an output when the controlsignal from its manual start input and its associated pilot device areboth true. This output will then serve as the input signal for moduleSCR which will also produce an output when the control signal from itsassociated pilot device is true. The output of module SCR then acts asthe input for normally closed contact module 9CR. This module acts in amanner different from modules 3LS and SCR in that it produces an outputonly if there is a false signal from the pilot device associated with itand a true signal from the previous module. Should this condition exist,then module 9CR provides an output which serves as an input signal forthe output module lCR. The output module produces an output signal levelin response to the input signal,

which is capable of controlling a machine function by way of elements(not shown) familiar to those skilled in the art such as solenoids,relays, coils, motor starters and others. The output signal istransmitted by control output lines 43 connected to the output modules32. Thus we see that modules 3L8, SCR, and 9CR all function in AND logicto produce an output signal.

A logic OR function is provided by wiring the output of 3CR normallyopen contact module in bar 26b to the input of contact module 9CR in bar260 by a connecting wire 27. This allows the output from the lCR outputmodule to be also activated by the 3CR and 9CR contact modules ANDedtogether.

Contact modules 2PS and 4CR in bar 260 are ANDed together to provide aninput to output module 2CR, the output of which controls another machinefunction.

For an electrical system the vertical bars 33 can distribute the twosides of an appropriate voltage supply (not shown). The modules can thenbe electrically wired together and grounded to the bars 26 by meansfamiliar to those in the electrical control art. For a .fluidic systemthe vertical bars 33 function as the air supply lines which feed thecontact modules through power output points 21 in the bars 26 throughmanifolds which are well known to those in the fluidic arts.

Referring now to FIG. 3, the normally-open contact modules.28 comprisean AND gate 40, which can be electrical or fluidic. The gate 40 inputsignal is applied to an input 42 by way of module connecting lines 41,external switches, or from the mounting bar 26. The

control signal is applied to a control signal input 44 by way of theproper signal from lines 25 originating from the pilot devices 19 orother contact modules. When both the input 42 and the control 44 providea true signal to the AND gate 40, the output is activated andtransmitted through the output line 46 to the module connecting lines41. This output also activates the module contained indicator 31 whichis directly connected in the output line 46 and is activated only by theoutput of its corresponding module.

Referring now to FIG. 4, the AND gate 40 in conjunction vvith a signalinverter 48, which changes a true signal to false and vice versa,comprises the normally closed contact module 30. The connection andoperation is similar to the module 28 described in reference to FIG. 3with the exception of the control signal being inverted. In this module,the control signal from line 25 is connected to the inverter 48 whichprovides a signal opposite to the one supplied by the pilot device 19 tothe gate input 44. Thus the gate 40 output is activated when a truesignal exists at input 42 and a false signal exists at control signalline 25.

Referring now to FIG. 5, the output module 32 includes a driver 50. Thefunction of the driver 50 is to convert the input signal received at adriver input 52 from the module connecting line 41 thus providing anoutput through driver output line 54 whichis able to activate a machinecontrol through output lines 43. For a fluidic system, the driver 50 canbe a booster relay, pressure/electric transmitter, or any other fluidicsignal modifying device. For an electrical system, the driver 50 can bea DC to AC converter, electric/pneumatic transmitter, a DC amplifier, orany other similar electrical signal modifying device.

Obvious modifications will occur to those familiar with the art. As anexample a timer may be connected into the control system to delay therelaying of an output signal to the next associated device. This timermay be incorporated as a separate module within the ladder network 20 oras a device external to the ladder network 20. Similarly a memory deviceto hold the input signal within the ladder network 20 until reset'occurscould be incorporated externally or appear as a separate module withinthe ladder network. It is intended that this description not be limitedto the embodiment described, but to be inclusive of the mentionedexamples as well as all other similarly obvious modifications.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A sequence control system comprising:

a ladder shaped structure having means for conducting power along thestruts of said structure;

a plurality of contact modules operationally mounted to the struts ofsaid structure for executing logic functions in response to inputsignals to said control system;

an output module operationally mounted to a strut of said structure forproviding an output signal from said control system in response to theexecuted logic of said contact modules; and

said contact modules and said output module having appropriate markingsto display and function in the manner of a ladder drawing of saidsequence control system.

2. A sequence control system as set forth in claim 1 including means,individually mounted to said contact and output modules, for indicatingthe output condition of each of said contact and output modules.

3. A sequence control system as set forth in claim 2 wherein saidindicating means is directly connected to the output of said outputmodule to provide indication whenever an output signal appears from saidoutput module.

4. A sequence control system as set forth in claim 3 wherein saidcontact modules are logic AND gates.

5. A sequence control system as set forth in claim 4 wherein a supplypower source is distributed to the struts of said structure for parallelconnecting said con-' tact modules on each strut of said structure.

6. A contact module for providing and displaying switching functions ina sequence control system comprising;

a module body;

an input signal connection located at a side module body;

an output signal connection located at a side of said module body;

a control signal connection located at a side of said 'module body; and,

of said a legend located on a face of 'said module body ina logical ANDcombination of signals to said input signal connection and said controlsignal connection.

8. An output module for providing an output from a sequence controlsystem to control an output element comprising:

a module body;

an input connection located at a side of said module body;

an output connection body; and

a legend located on the face of said module body indicating inputconnection line connected to an alphanumeric representation of saidoutput element controlled.

9. A module mounting frame, in the form of a ladder,

for use in a sequence control system comprising;

a set of substantially parallel main structures to which a drivingpotential is supplied to power said frame;

a plurality of substantially parallel module mounting members orientedbetween and substantially per pendicular to said main structures; and, I

said mounting members providing paths for conducting the potentialapplied to said main structures when modules are mounted on saidmounting members.

located at a side of said module

1. A sequence control system comprising: a ladder shaped structurehaving means for conducting power along the struts of said structure; aplurality of contact modules operationally mounted to the struts of saidstructure for executing logic functions in response to input signals tosaid control system; an output module operationally mounted to a strutof said structure for providing an output signal from said controlsystem in response to the executed logic of said contact modules; andsaid contact modules and said output module having appropriate markingsto display and function in the manner of a ladder drawing of saidsequence control system.
 2. A sequence control system as set forth inclaim 1 including means, individually mounted to said contact and outputmodules, for indicating the output condition of each of said contact andoutput modules.
 3. A sequence control system as set forth in claim 2wherein said indicating means is directly connected to the output ofsaid output module to provide indication whenever an output signalappears from said output module.
 4. A sequence control system as setforth in claim 3 wherein said contact modules are logic AND gates.
 5. Asequence control system as set forth in claim 4 wherein a supply powersource is distributed to the struts of said structure for parallelconnecting said contact modules on each strut of said structure.
 6. Acontact module for providing and displaying switching functions in asequence control system comprising; a module body; an input signalconnection located at a side of said module body; an output signalconnection located at a side of said module body; a control signalconnection located at a side of said module body; and, a legend locatedon a face of said module body indicating input and output connectionlines connected to a contact, the normal state of said contact, and theelement which provides said control signal.
 7. A contact module as setforth in claim 6 wherein said output signal connection is powered inresponse to a logical AND combination of signals to said input signalconnection and said control signal connection.
 8. An output module forproviding an output from a sequence control system to control an outputelement comprising: a module body; an input connection located at a sideof said module body; an output connection located at a side of saidmodule body; and a legend located on the face of said module bodyindicating input connection line connected to an alphanumericrepresentation of said output element controlled.
 9. A module mountingframe, in the form of a ladder, for use in a sequence control systemcomprising; a set of substantially parallel main structures to which adriving potential is supplied to power said frame; a plurality ofsubstantially parallel module mounting members oriented between andsubstantially perpendicular to said main structures; and, said mountingmembers providing paths for conducting the potential applied to saidmain structures when modules are mounted on said mounting members.